Record coffee harvests in Brazil, the biggest grower, are compounding a global glut of arabica used by Starbucks Corp. (SBUX) and Dunkin’ Donuts Inc.

Brazilian farmers will reap 50.8 million bags in 2013, a record for a so-called low-crop season, according to the median of nine analyst estimates compiled by Bloomberg. The harvest reached 55.9 million 60-kilogram (132-pound) bags in 2012, an all-time high for a peak year. Output usually drops in alternate years because of growing cycles. Prices may fall 14 percent to $1.311 a pound by June 30, the average of 14 predictions shows.

Futures slumped about 50 percent since May 2011, as the highest prices in 14 years spurred Brazilian farmers to boost supply. Their exports jumped 54 percent to $8.7 billion in 2011. The flood of beans has continued and stockpiles tracked by the ICE Futures U.S. exchange are headed for the biggest annual gain in more than a decade. Rising costs and concern that economies are slowing encouraged roasters and consumers to favor cheaper robusta beans.

Coffee growers in Brazil, the world’s largest producer, have harvested almost 25 percent of this year’s robusta crop, according to broker Flavour Coffee.

The country, which is the biggest grower of the arabica variety and ranks second in robusta production, will harvest 50.4 million bags of coffee in the 2012-13 season, the Ministry of Agriculture’s crop-forecasting agency, known as Conab, said yesterday by e-mail. Arabica output will total 38.1 million bags and robusta 12.3 million bags, it said. A bag weighs 60 kilograms (132 pounds).

“New crop arrivals keep improving,” the Rio de Janeiro- based broker said in a report e-mailed yesterday, adding that less than 15 percent of the robusta harvest was available because drying and peeling processes were not done yet.